https://fr.ivisa.com/grenada-travel-authorization 

 A Grenada Travel Authorization, also referred to as a Grenada Passport is an internationally recognized passport issued by the Grenada administration. It doesn't have any particular country information on it, but rather contains a request and entry destination. Only a Grenada Travel Authorization Certificate can be used to authorize travel beyond the territorial waters of Grenada. For some travelers, such a passport is essential when visiting Grenada. 

 A Grenada Travel Authorization is required for many reasons. These include travel to Grenada to visit family members or any other reason that makes travel to Grenada mandatory. For example, there are those who wish to visit Spain, Grenada's neighbor, for tourist purposes. In addition, tourists frequently fly to Grenada and then go back to Spain. Still others may need a Grenada travel authorization to visit the Grenada capital of San Juan de Dios. A valid passport is required for any of these reasons. A Grenada passport could be your ticket.

 But what if you were flying to Grenada to visit family and decide to stay? Would you still need a valid passport? That's what many travelers ask themselves when making this travel decision. Yes, you will still need a passport if you present a valid Grenada travel authorization, as mentioned above. Grenada doesn't have a consulate to Spain like its neighbors. 

 You must visit the Ministry of Foreign Affairs and the Consulate General of Grenada to obtain your passport. These offices are located at San Juan de Dios which is the economic center of Grenada. The Grenada travel authorization form can be obtained from these offices if you are present. You can also get a copy your passport from this office. You may also visit the consular office in Barcelona to apply for your passport if you prefer. 

 Once you have obtained your passport from the authorities it is time for you to visit the Granada Airport. At the airport's Air Traffic Control (ATC), they will verify your identity (including your Grenada Travel Authorization) and issue a temporary visa. To reach your destination, you will board an international or domestic flight. 

 You must carry your travel document and any additional required documents when traveling overseas. These include your passport, check-in information, itinerary, and any other items that indicate your intended travel. You may check in with the airline company before your flight if you are coming from a different destination than where you've purchased tickets. However, you should not check in unless you have your Grenada Travel Authorization or an itinerary in hand that includes all your destinations. You can also get a Grenada travel document in an emergency without requiring a visa. For more information on these, contact your local travel office.